Process for reclaiming soiled solvent in situ



Jan. 24, 1967 w, BLACK 7 3,300,405

PROCESS FOR RECLAIMlNG SOILED SOLVENT IN SITU Filed June 10, 1963 INVENTOR. Lawrence W B/acK W M V M A+ forneys United States. Patent C) 3,300,405 PROCESS FOR RECLAIMING SOILED SOLVENT IN SITU Lawrence W. Black, Irondale, Ala., assignor of twentyfour one-half percent to Joe Paradise, and twenty-four one-half percent to Harry D. Hester, both of Birmingham, Ala.

Filed June 10, 1963.5. No. 286,628 6 Claims. (Cl. 210-21 This invention relates to a process for reclaiming a soiled solvent in situ and more particularly to a process for recovering cleaning solvents which are positioned within a container whereby the articles to be cleaned are immersed in the solvent.

An object of myinvention is to provide a process for reclaiming soiled solvent wherein contaminants are removed from the solvent without having to transfer the solvent to other cleaning apparatus, thereby eliminating the cost of transferring the solvent as well as reducing the time and labor required to'reclaim the solvent.

Another object of my invention is to provide a solvent recovery process of the character designated which is carriedout without the necessity of providing heat and distilwhich an aqueous stratum above the solvent is treated whereby the specific gravity thereof is increased to a point that it moves downwardly through the solvent to a position subjacent the solvent whereby the aqueous stratum along with any sludge or other contaminants may be readily removed from the bottom of the solvent container with a minimum loss of solvent.

Another object of my invention is to provide a process for reclaiming solvents of the character designated in which there is an effective removal of salts which. are soluble in the water phase and bring about undesirable emulsification of the aqueous stratum and the solvent.

Another object of my invention is to provide a. process of reclaiming solvents of the character designated in which the materials added to the aqueous stratum to increase the specific gravity thereof also aid in cleaning up the solvent as it passes downwardly therethrough and at the same time leaves a residue which increases the pH of the residual solvent composition, thereby. reducing the amount of additives required to restore the cleaning container to its operating condition.

A still further object of my invention is to provide a process for reclaiming solvents of the character designated which is extremely simple to carry out 'by unskilled labor and one which may be carried out in conventional apparatus with substantially no change therein.

Heretofore in the art to which my invention relates, various processes have been devised for recovering solvents which are employed to clean articles, such as aircraft engines, marine engines and the like. However, such processes have usually involved transfer of the cleaning container or dumping the contents of the cleaning container into a suitable tank for transfer to distillation ap paratus for subsequent recovery. After the solventhas been recovered, the solvent must then be stored in storage tanks or the like until it is ready to be transported back to the cleaning container. This not only interrupts the operation of the cleaning apparatus but at the same time requires considerable expense in the transportation and handling of the solvent. Also, the distillation of the solvent is expensive and at the same time soaps, metal salts and other high-boiling point materials are lost, thereby requiring additional soaps to restore the cleaning container to its operating condition.

Briefly, my improved process for reclaiming soiled solvent comprises adding to an aqueous stratum above the soiled solvent a solution which is substantially insoluble in the solvent and has a specific gravity greater than the aqueous stratum whereby the specific gravity of the aqueous stratum is increased to a point that the aqueous stratum moves downwardly through the solvent to a position beneath the same. The aqueous stratum thus inverted is removed along wit-h any contaminates, sludge and the like which settles beneath the solvent.

Apparatus which may be employed to carry out my improved process is illustrated in the accompanying drawing, forming a part of this application, in which:

FIG. 1 is a vertical sectional view through a cleaning container having unused solvent and aqueous stratums therein; and,

FIG. 2 is a vertical sectional view through the cleaning container after the aqueous stratum has been inverted.

Referring now to the drawing for a better understanding of my invention, I show a cleaning container 10 which preferably has a downwardly converging bottom wall 11. A discharge valve 13 comunicates with the lower end of the container 10 whereby the contents adjacent the bottom of the container 10 may :be removed through a suitable conduit 14. To reduce agitation adjacent the lower end of the cleaning container 10 I provide transverse plates 16 which are spaced vertically from each other. A plurality of openings 17 are provided in the plates 16 to permit free flow of liquids and other materials therethrough. To further aid in reducing agitation, vertically extending plates 18 may be provided adjacent the lower end of the cleaning container 10, as shown.

Conventional type solvents are employed in the cleaning container 10, such as the chlorinated solvents which are employed for cleaning aircraft engines, marine engines and the like. The sol-vents usually comprise methylene chloride, creosote-like materials, soaps, corrosion inhibitors, sodium chromate, sodium dichromate, wetting agents and the like. The solvent is water immiscible and is indicated generally by the" numeral 19. That is, the solvent has substantially lower water solubility.

Positioned above the water immiscible solvent 19 is an aqueous stratum 21. The aqueous stratum 21 thus serves as a seal for the solvent to thereby prevent evaporation of the solvent. Not only does this prevent loss of solvent through evaporation, but eliminates a health hazard due to the fact that the vapors from the solvents are very toxic. The stratum of water thus assumes the position indicated ,by the bracket 22.

In the normal operation of the cleaning apparatus,

- there is a gradual build-up of soils to contaminate the cleaning solvent 19 and thus decrease the efficiency of the operation. There are certain contaminants that have in the past caused considerable loss by corrosion of the parts in the cleaning container. That is, aluminum and magnesium articles corrode very rapidly when they are positioned in a cleaning container where the solvent and seal have emulsified whereby most of the solvent is adjacent the top of the cleaning container while the corrosive poisons are located adjacent the middle and bottom of the container. It has been the usual practice to takesamples adjacent the top of the cleaning container to determine whether or not the contents thereof were at operating level. This method of testing has been deceptive due to the fact that such tests do not give an inversion of the aqueous stratum 21 by manipulation of the specific gravity of the aqueous stratum. The specific gravity of the aqueous stratum 21I'is increased by the addition of a suitable metal salt, such asflsoclium hydroxide, potassium hydroxide, or sodium, Ichromate The metal salt added must be compatible with the, equipment and the materials cleaned or processed therein. Since the aqueous stratum Zlusually has a certain amount of various dissolved salts and soluble soils' therein, the amount of sodium hydroxide or other metal salt required will depend upon the existing specific gravity of the aqueous stratum prior to, theaddition of them'etal salt. This can be easily determined b y ahydrometer in a manner well understood in the art. Upon increasing the specific gravity ot the aqueous stratum 21, it settles slowly through the solvent '19 to a position beneath the solvent'whereby the aqueousstr-atum assumes the position indicated :by"thefbrac ket '23. Upon addition of the sodium hydroxide or'the like,itlie soil solubility of'theso lvent1 9 isfreducedfwhereby a flocculent precipitate settles to the bottom of the tainer 10. The specific gravity of the aqueous stratum 21 is preferably "increased whereby it ranges from @P- proximately 1.10 to, 1.24. A slight amount of agitation aids in separation of thesolvent 'from the sludge and hours whereupon the aqueous stratum and contaminants carried therein are then ready'for removal. f To "remove a the contaminants and the aqueous stratum from the lower portion of the container 10, the valve 13 ,i's opened where upon the sludge and other contaminants carried by the inverted aqueous stratum are removed to thereby leave only the solvent and valuable soaps carriedtherein with in the cleaning container 10,. If desired, jthefcontent's Not only does the inversionof the aqueous stratum I 21 and subsequent removal thereof through thewalve 13 of the cleaning container may be permittedto settle for g,

remove sludge accumulations and precipitated flocculent 3 materials, but the water increases the solubility of certain soils and dirty sludge whereby upon inverting the water phase, thesludge is removed more effectively by drainage. It is' these soluble salts in the water phase which bring about undesirable emulsification of the aqueous and solvent stratums in the cleaning container,

, and the resulting corrosion of magnesium and aluminum parts.

When .the materials discharged through the valve" 13 equal the volume of the orignal aqueous stratum or in-' dicate the presence of the solvent, the valve-13 is closed and a new aqueous stratum 21 is added whereby it remains at the top of the solvent 19. The cleaning container 10 is then ready for final solvent and corrosion inhibitor additions whereby the solvent cleaner is brought back to its original operating condition. I s

The solvent may be further cleanedflby adding from 2 to 4 ounces of sodiumchromate or sodium dichromate per each gallon of water in the aqueous stratum 21 at the same time the caustic is added andis' removed the inverted water phase. The pH of the contents of the cleaning container is readjusted whereby the pH of the final solvent ranges from approximately ll to 11.6 and preferably 11.3. The chromate content' i n the final aqueous stratum is' adjusted whereby it ranges from 1" to 4 ounces per gallon.

After inversion of the aqueous'stratum the solvent phase comprises separate str-atums of dilferent type solvents. For example, where methylene chloride and cresylic solvents are employed the methylene chloride would be above the cresylic solvents. Accordingly, any layer of solvents may be removed-from the container by providing discharge valves 24 at selected elevations alongside the container. This is desirable where one solvent stratum'becomes' more contaminated than other stratums.

Also,-'after' inversion, the soaps form a stratum 'adjacent and -above'the invertedaqueous stratumi Accordingly, the soap stratum may be removed, if desired, after removal of the aqueous stratum. This is especially desirable when the soaps have been used to the extent that they are no longer useful. Upon addition of 'the'caustic solution, a greater quantity of-" t-he' caustic is absorbed bythe -soa'p and cresylic stratums than by-the chlorinated solvent' phase; "This results in the chlorinated solvent being more concentrated adjacent the top ot-the container. This further aids in the removal of less expensive stratums when they arecontaminated following the removal--of tlie aqueous stratum. I Th'e additi'o'n of'the caustie'solution to the water phase ""can-be -niadein twds'teps; First, the caustic solution" is added to cause the-water phase to-be equal in specific gravity to=that of the lower -solvent phase. A further addition of caustic solution is then made to' invert the water 'ph-ase.-'- This procedure would minimize {agitation necessary'tomix alarge container of -solvent and at the same time it would cause a maximum pre'cipitation of solids which are. more soluble-'inthe solvent phase. This "is applicable "to "vapordeg-reaser -solvent refining where 'microcrystalline w'axe's; beeswax and various plastics are 'dissolved in;the"solventz L "From the foregoing'it will be seen that 'I' have devised an improved process for restoring within a cleaning-eontainer soiled solvenfhaving"substantially 'low water solu- --bility'an d 'havin'ganaqueous'straturn above the same. By adding a 'metal saltg such as sodium-hydroxide and the like, to' ihcrease' the specific gravity-of the aqueous stratum above th'e soIve'nt, -I bring about a -thorough' mixing of the water and the'wa'te'r immiscible solvent to thereb'y reduce the solubility -of the contaminants carried :by :the solvent. Also; by increasing --the' specificf'gravity -of the: aqueous stratum whereby the aqueous s'trat'um'is invertedlland 'rnoves' downwardly thro'ughthe solvent'tothe' bottom of thecontainer, -p'recipitated'materials also. goto the bottom whereupon they are easily removed along with the inverted aqueous stratum." Also, the presence of hydroxides and chromates decrease the dissolved contaminants in the solvent phase and act as a second cause for certain solvent dissolved solids to precipitate to the lower inverted water phase. Als'o, by inverting the aqueous stratum, the water increases the solubility of certain solids and dirty sludge whereby a more effective removal of'the sludge and other foreign materials is obtained. Furthermore, by reclaiming" the soiled solvent 'in' situ, I eliminate entirely'--'the necessity' of dumping 'the 'contents of .the cleaning container or transferring thesame to other recovery appa ratus'gsuchas distillation apparatus-and. the "likeftherehy' notonly reducing the overall cost of the recovery, but atthe same time reducinglthe time thatthe cleaning container 'is" out of operation, and-reducing'equipment investment-'- -'i '5 I wish it to be understoodthat Ido not/desire to be -'limited'to the exact details of the process shown: and described, for obvious modifications-will occ'urfto zalperson skilled in the art.

What I claim'is: i i

1. The process of reclaiming in, situ in'a cleaning contairier'a soiled organic solvent having'a specific gravity greater than water"-and' having substantially"low'water 1 solubility and having an aqueous stratum above "the same --whicl r coin'prise's thesteps-oft Y 1 u ,1:

' (ajgaddirig to saidaqueoiis' stratum an amount-' of 'a solution of a compound selected from the group consisting of sodium hydroxide, potassium hydroxide and sodium chromate which is substantially insoluble in said solvent and will decrease soil solubility in said solvent and has a specific gravity greater than said aqueous stratum to increase the specific gravity of said aqueous stratum to a point that said aqeous stratum moves downwardly through said solvent to a position beneath said solvent whereby solvent dissolved soils are precipitated and moved with said aqueous stratum to a position beneath said solvent to the bottom of the container, and

(b) removing said aqueous stratum and said soils from the bottom of the container after they have moved to a position beneath said solvent and after a time interval of at least one and one-half hours has lapsed after introduction of said solution.

2. The process of reclaiming a solvent as defined in claim 1 which includes the further steps of:

(a) adding additional solvent constituents to the contents of the cleaning container to form a predetermined composition, and

(b) adding an aqueous stratum above the final solvent composition.

3. The process of reclaiming a solvent as defined in claim 2 in which the pH of the final solvent ranges from approximately 11 to 11.6.

4. The process of reclaiming a solvent as defined in claim 2 in which the pH of the final solvent is approximately 11.3.

5. The process of reclaiming a solvent as defined in claim 2 in which from 1 to 4 ounces of a chromate salt selected from the group consisting of sodium chromate and sodium dichromate is added to the aqueous stratum above the final solvent composition for each gallon of said aqueous stratum above the final solvent composition.

6. The process of reclaiming a solvent as defined in claim 2 in which a quantity equal to the volume of the water phase before inversion is removed adjacent the bottom of the solvent to remove contaminates which settle to the bottom thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,585,456 5/ 1926 Allinson 208-179 1,917,489 7/1933 Bizzoni et a1 134-2 MORRIS O. WOLK, Primary Examiner. 

1. THE PROCESS OF RECLAIMING IN SITU IN A CLEANING CONTAINER A SOILED ORGANIC SOLVENT HAVING A SPECIFIC GRAVITY GREATER THAN WATER AND HAVING SUBSTANTIALLY LOW WATER SOLUBILITY AND HAVING AN AQUEOUS STRATUM ABOVE THE SAME WHICH COMPRISES THE STEPS OF: (A) ADDING TO SAID AQUEOUS STRATUM AN AMOUNT OF A SOLUTION OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF SODIUM HYDROXIDE, POTASSIUM HYDROXIDE AND SODIUM CHROMATE WHICH IS SUBSTANTIALLY INSOLUBLE IN SAID SOLVENT AND WILL DECREASE SOIL SOLUBILITY IN SAID SOLVENT AND HAS A SPECIFIC GRAVITY GREATER THAN SAID AQUEOUS STRATUM TO INCREASE THE SPECIFIC GRAVITY OF SAID AQUEOUS STRATUM TO A POINT THAT SAID AQEOUS STRATUM MOVES DOWNWARDLY THROUGH SAID SOLVENT TO A POSITION BENEATH SAID SOLVENT WHEREBY SOLVENT DISSOLVED SOILS ARE PRECIPITATED AND MOVED WITH SAID AQUEOUS STRATUM TO A POSITION BENEATH SAID SOLVENT TO THE BOTTOM OF THE CONTAINER, AND (B) REMOVING SAID AQUEOUS STRATUM AND SAID SOILS FROM THE BOTTOM OF THE CONTAINER AFTER THEY HAVE MOVED TO A POSITION BENEATH SAID SOLVENT AND AFTER A TIME INTERVAL OF AT LEAST ONE AND ONE-HALF HOURS HAS LAPSED AFTER INTRODUCTION OF SAID SOLUTION. 